Update: Romney drops out

Senator John McCain fought for the backing of the Republican Party's conservative base in a fiery speech Thursday just after rival Mitt Romney quit the race, clearing his path to the White House.

Addressing the annual gathering of fervent Republican activists, McCain sought to shore up his conservative credentials and allay fears over his stand on some key issues as he seeks the party's presidential nomination.

"It is my sincere hope that even if you believe I have occasionally erred in my reasoning as a fellow conservative, you will still allow that I have, in many ways important to all of us, maintained the record of a conservative."

With former Massachusetts governor Romney dropping out of the race on Thursday after a slew of poor Super Tuesday showings, McCain's path to the Republican ticket is suddenly a lot clearer.

But recognizing the crucial support he needs from the party's conservative base to win the nomination for the November elections, the Vietnam war veteran called for its backing in defeating the Democrats.

"I am acutely aware that I cannot succeed in that endeavor, nor can our party prevail over the challenge we will face ... without the support of dedicated conservatives."

Peppering his speech with references to former president and Republican icon Ronald Reagan, McCain set out a platform of tough stands on various issues from abortion, to tax cuts and his unwavering support for the Iraq war.

The Arizona senator, 71, has a solid conservative voting record, but has enraged the key constituency with his stands on immigration reform, by initially opposing Bush's huge tax cuts and on campaign finance measures.

But addressing the immigration issue head-on, McCain told the Conservative Political Action Conference (CPAC) that he had "stood my ground aware that my position would imperil my campaign."

His intention had been to restore border controls, he said, vowing that as president he would work first to secure the frontiers before trying to tackle illegal immigration.

"I will not obscure my positions from voters who I fear might not share them. I will stand on my convictions, my conservative convictions and trust in the good sense of the voters," McCain said.

And he pledged to offer voters "a clearly conservative approach to governing," as the crowd warmed to his speech after an initially chilly welcome.

Romney earlier quit the White House race after spending millions of dollars of his personal fortune on a campaign which failed to fire up the party faithful.

"This isn't an easy decision, I hate to lose," Romney told the conservative conference, saying he was suspending his campaign to avoid a damaging, divisive race which could hand the November elections to the Democrats.